1. Field of the Invention
The present invention relates to a method for the manufacture of glass, in particular for glass fibers for optical communications through deposition of glass particles on a substrate from a flame.
2. Description of the Prior Art
SiO.sub.2 for glass fibers used in optical communications devices can be produced through flame hydrolysis, as is known. Known methods are the OVD-method and the VAD-method in which doped SiO.sub.2 is deposited in the form of a securely adhering powder on the cladding surface, or the end face of a rotating substrate rod. In the case of the first-cited method, the flame and the substrate rod are moved relatively to one another in longitudinal direction of the substrate rod, and the dopant concentration is chronologically varied in the fuel gas generating the flame, whereas position and concentration, in the case of the second-cited method, are not changed. Common to both methods is the limited yield of the deposition, for approximately 50% of the employed SiCl.sub.4 is lost as SiO.sub.2 with the exhaust gas and must be filtered out. The effective mechanism in the case of the deposition is thermophoresis, which leads to the migration of the glass particles disposed in the submicron range transversely to the gas stream from the hot center of the flame to the cold substrate.